Silicon stacked interconnect technology (SSIT) involves packaging multiple integrated circuit (IC) dies into a single package that includes an interposer die and a package substrate. Utilizing SSIT expands FPGA products into higher density, lower power, greater functionality, and application specific platform solutions with low cost and fast-to-market advantages. While SSIT products provide several advantages, the logistics associated with tracking such SSIT products becomes quite challenging.
Tracking components of the SSIT product, particularly the interposer die of the SSIT product is important for several reasons. Tracking an interposer die to its wafer of origin, its location on the wafer of origin, and its wafer lot, allows defective interposer dies to be easily identified and further provides quick feedback for identifying other potentially defective SSIT products that may be associated with the defective interposer die. Furthermore, particular characteristics for interposer dies (e.g., leakage current) may be easily identified to facilitate establishment of performance criteria for SSIT products.
Conventional methods for tracking integrated devices use active electrical circuits within the integrated device. For example, integrated devices may include fuses which may be blown to create unique identifiers for the integrated device. Currently, however, interposer dies of an SSIT product are passive components that include only metal interconnects and do not include any active circuitry. Even if interposer dies of an SSIT product are implemented with active circuitry for future use, the use of polysilicon or metal fuses for identification is impractical because of its high costs. Besides having a higher cost, the fuse circuits will also require additional die area. Moreover, fuse circuits will also have potential design, process defect and variation issues associated with technologies that have critical dimensions less than 65 nm. As such, existing tracking methods cannot be used to track interposer dies of an SSIT product.